(1) Field of the Invention
The present invention relates to structures of lens sheets included in display panel apparatuses having electroluminescence (hereinafter referred to as EL) elements.
(2) Description of the Related Art
As a conventional technique to improve light-extraction efficiency in a display panel apparatus including light emitting elements such as organic EL elements, a lens sheet having lenses is provided in a direction in which the light emitting elements emit light.
FIG. 1 shows an example of a structure of a conventional lens sheet.
A conventional lens sheet 500 shown in FIG. 1 includes a sheet base 501 in sheet form and lenses 502 protruding from a surface of the sheet base 501.
The lens sheet 500 is positioned in the light emitting direction of a substrate which has light emitting units including organic EL elements.
In positioning the lens sheet 500 with respect to the substrate as above, it is necessary to align the substrate and the lens sheet 500 with accuracy.
Specifically, with respect to the substrate, the lens sheet 500 needs to be positioned so that the lenses 502 are located precisely above the respective light emitting units in FIG. 1.
For this reason, the conventional lens sheet 500 has an alignment mark 503a and an alignment mark 503b, for example. The alignment mark 503a and the alignment mark 503b protrude in a direction which is the same as a direction in which the lenses 502 protrude from the surface of the sheet base 501, and these marks function as markings for aligning the lens sheet 500 with the substrate.
In joining the lens sheet 500 having the above structure to the substrate, positioning is performed so that, for example, in FIG. 1, the right end of the alignment mark 503a matches the right end of an alignment mark 603a provided on the substrate.
Furthermore, this positioning is followed by checking whether the right end of the alignment mark 503b matches the right end of the alignment mark 603b provided on the substrate in FIG. 1, for example.
These positioning and position checking are performed using results of analysis on data of images captured from above in FIG. 1, for example.
A technique related to a lens sheet having such protruding alignment marks has also been disclosed (see Japanese Patent Application Publication No. 11-352468).